hydrocarbons excessive fail

[paul66beetle]

Well mine was running rough again on Sunday. So decided to have another look after replacing a ton of hoses. I have found a petrol leak on the left hand carb. Quite a big leak with a strong smell of fuel. Looks like a carb rebuild

[weimarbus]

also be aware that if the choke pull down units have failed you will be drawing in air, pierburg has one for the choke and one for the second barrel, if you suck on a piece of tube connected to either and put your tongue on the end to block it and it returns to its rest possition then the diaphram is shot and will draw air in causeing high hydrocarbons due to weak mixture

[paul66beetle]

also be aware that if the choke pull down units have failed you will be drawing in air, pierburg has one for the choke and one for the second barrel, if you suck on a piece of tube connected to either and put your tongue on the end to block it and it returns to its rest possition then the diaphram is shot and will draw air in causeing high hydrocarbons due to weak mixture

Will be looking for a rebuild kit, like you said it's bound to be drawing air in if petrol is leaking, thus no longer sealed.

JK have the kits on back order for both carbs and Heritage have the kit per side at £25 hmmm.

[iangreentree]

Hi all, newbie on here....
My 1980 2ltr Aircooled T25 failed its MOT. Mainly due to excessive carbon monoxide emissions and also hydrocarbon emissions which apparently came in at over 3000. I'll could try changing the air filter but I reckon this would be the equivalent of turning up to an earthquake with a dustpan and brush!

Could I get a fault finding check-list from you fine people?

Much peace
Ian.

[paul66beetle]

I think the main cause of high HC and lean running is an air leak.

Check the carbs and associated pipes for air leaks especially the balance pipe and associated braided hoses. Do not forget that the braided hoses have rubber underneath and the braiding might look ok but might be leaking like a sieve.

Also possible that the air could be leaking from the servo end at the front and the pipe runs through a few joins and joins up with the carb. Check the common joins and does it feel like you have lost your servo assisted brakes?

Check the carbs for any leaks, including fuel & air.

You should be able to use carb cleaner to find any leaks, spray around the joins when engine is running and see if the engine runs differently. This will help find any air leaks.

[iangreentree]

Cheers @paul66beetle

I've had a look and come up with 2 Possibilities....

The hose is connected under the right carb (poss leak!) ....


These images show the right carb which i don't think the valve look healthy and i think fuel is getting in to the filter on the right handside.

[iangreentree]

Should I be concerned about the right carb judging by the photos?

Cheers.

[paul66beetle]

Should I be concerned about the right carb judging by the photos?

Cheers.

I don't think so. I think its possibly a case of cause and affect. I think if you manage to seal all the air leaks and getting it sucking as it should and tuned then it might look better. Its logical to fix the air leaks first and its usually the simple things.

I've found a definite petrol leak coming from my left carb, so logical to rebuild the gaskets. I replaced the hoses and T pieces already but they needed to be done anyway as do yous by the looks of it.

[iangreentree]

Thanks Paul66beetle, It makes sense and very helpful. I'll aim to bring the ratio of Gaffer tape Vs engine down..

[paul66beetle]

Thanks Paul66beetle, It makes sense and very helpful. I'll aim to bring the ratio of Gaffer tape Vs engine down..

You can buy the replacement T pieces and elbows, but I have found that they don't fit that snugly. Probably as they are aftermarket as opposed to OEM

http://www.justkampers.com/021-129-637- ... odels.html" onclick="window.open(this.href);return false;

so you might want to get some decent hose clips to seal them...my preference would not be jubilee clips as they tend to pinch and not form a proper circle if that makes sense.

[xpress]

so I had this emissions mot thingy to do.

adjusted co2 mixture to about 2.5. better than 5.6!

I can see why rev says it's not an exact science.

at 1.9 it was a bit rough idling.

does anyone have a classic engine that runs at 1.5 co2?

my spark looks a bit orangey yellow at the plug. ideally should be blue. could the coil need replacing? test voltage at battery and work way forward testing coil and clean contacts in between?

cap rotor plugs and leads have all been replaced.

would you in theory do well to adjust the mixture if you replaced old plugs for new, old coil for new, old battery for new?

more spark, less co2, richer mixture, better burn.

weaker spark. more air. leaner mixture. better co2 ratio. better burn?

[kevtherev]

colour tune.. it's ok, hit and miss..
orange yellow flame means too weak.. or too rich.??
I had one once and no matter what I adjusted it remained blue.

I would much prefer to use a gas anilyser... the results are very accurate.

[xpress]

hey rev. I didn't use color tune I used a co2 analyser. the spark colour I was referring to was with the plug earthing onto something in the van and observing the colour of the spark. ehat co2 reading do you manage to get rev with a smooth idle?

[kevtherev]

Mines been on gas for several years; I have forgotten what it was on petrol.
CO not CO2 is the value adjustment is made from.

[xpress]

co2. the 2nd reading of the coca cola soda stream.